Buphendra,
The computation is actually more complex than this, but the results are the same. For the sake of sharing, here is the full explanation 🙂
If you want to use SFH 1×1, then you must apply a threshold of 12% :
22 ARFCN – 10 BCCH ARFCN – 1 Guard
= 11 ARFCN available
11 ARFCN * 12% = 1.3 (approx)
This magic number “1.3” means you should have an average of 1.3 hopping TRX per sector, therefore your max BTS config should be 2/2/3.